Because the mid-sole material of an athletic shoe takes a pounding, it eventually loses its ability to provide your child's foot with adequate support or cushioning. The increased stress to the foot, leg and related soft tissue and bone structures, over time, can lead to an overuse injury [2] such as shin splints [3] that could put your child on the sidelines.

But how do you know when to replace your child's shoes?

One way is to look for tell-tale signs that the mid-sole is losing its cushioning ability, says Alana Cioffi of New Balance, such as wrinkles in the mid-sole and uneven wear patterns of the bottom sole.

Another is to consider replacing your child's shoes on a schedule:

• Running shoes [4]: Every 350-500 miles of running.
• Shoes for other aerobic sports: Around 300 hours
• Court (tennis [5], basketball [6], volleyball [7]) shoes: Every month (for those playing 5-6 times per week) or every 3 to 4 months (for those playing 2-3 times per week)

Buying new shoes [8] is thus a relatively cheap investment in preventative medicine.